ST_Orientation — 确定曲面方向
integer ST_Orientation(geometry geom);
integer ST_Orientation(
)
该函数仅适用于多边形。如果该多边形逆时针方向，则返回-1；如果该多边形顺时针方向，则返回1。
可用性：2.1.0
This method needs SFCGAL backend.
This function supports 3d and will not drop the z-index.
This method needs SFCGAL backend.
This function supports 3d and will not drop the z-index.